The general goals of the proposed research are to: (1) Investigate whether 24-hour Hotter monitoring can feasibly be added to biodemographic surveys and whether the Holler information contributes to better measurement of physiological toll and understanding of the causal mechanisms that link individual characteristics and socio-economic conditions with health and survival, and (2) Provide a database that can be used by ourselves and others to shed light on the impact of stress on the poor health and high mortality of middle-aged and elderly Russians. The proposed research builds upon a promising small-scale pilot project, the 2002-2003 Moscow Pilot Study. To pursue these general goals we propose to conduct a demographic and health survey of 2,000 men and women aged 55+ who reside in Moscow. The study questionnaire will include information about early life conditions, socio-economic status, health and quality of life, health behaviors, physical and cognitive ability, and psychological stress. Data on various biomarkers reflecting multi-system body functioning will be collected. Twenty-four-hour Holter monitoring will provide multi dimensional time series reflecting heart rate variability, arrhythmia events, sleep and other circadian (day- night) characteristics. We propose to study these data, using standard statistical methods of regression analysis, with a focus on determining the incremental value of Holter monitoring as an additional source of information in biodemographic research. We plan to conduct a follow-up interview of all survey participants approximately 2.5 years after the first interview and to study these longitudinal data, using standard statistical methods of survival analysis, with a focus on determining the incremental value of Holter information to predict morbidity and mortality. Finally, we propose to prepare and promptly release a user- friendly dataset that includes all the data we collect. The study will attempt to determine the most informative parameters for predicting health risk for future use in research and public health practice.